One of my favorite demonstrations as a physics teacher was to put a student on a frictionless stool and spin them around with their legs extended out in front of them. I would then tell them to pull in their legs. When they did that, their angular velocity increased dramatically—they spun faster. We see this when a spinning figure skater pulls in their arms and legs causing a dramatic increase in their rotational speed. This is an excellent demonstration of the conservation of energy and angular momentum. It is also a design feature that enables a wide variety of living things to fly without prohibitive losses of metabolic energy. We call it God’s elevator.
Instead of solids, what happens if the material that is spinning is a fluid – water or air for example. When water goes down the drain in your sink, it picks up speed as it gets near the center. In the very center, there won’t be any motion at all. In a hurricane, warm air is rising in the center, and as air rushes in to replace the rising air, it increases in speed. The center with no air rushing in is the eye of the hurricane, and the maximum velocity is in the wall near the eye.
A less dramatic example of the vortex is the convection cell on a hot summer day. The Sun heats the ground which then heats the air near the ground. The heated air rises, and as it does, the edges of the air are cooled by contact with the colder air around it. This creates a doughnut-shaped thermal vortex that rises to make an invisible, energy-saving elevator for any organism that can get into the doughnut. What this means is that an animal like a hawk does not have to beat its wings and spend enormous energy to soar to a high elevation. This is a huge saving in metabolic energy. An amazing number of living organisms use God’s elevator to get high into the sky and travel very long distances.
Charles Darwin, while sailing on the Beagle, noticed a mass of spiderlings 60 miles off the South American coast. These organisms are terrestrial creatures, but they were able to travel enormous distances by using vortices. Moths use vortices to make journeys from where they are to new areas.
Recent studies of birds have shown that the wings of a bird create a vortex system which is like a ladder. There is almost no lift produced by the bird’s wings on their upstroke, but the downstroke creates a vortex. That vortex combines with vortices on the wing tips making a ring. The combination of these ring vortices makes a zigzagging ladder-like system which lifts the bird. This allows the bird to use a smaller amount of energy than if it merely powered itself through the air. That is why the birds in your backyard fly in a zigzag pattern rather than a smooth path.
Blackfly larvae that live on the bottom of a stream position themselves so that water flowing over the bottom of the tube-shaped larva goes faster creating a low pressure rising along their bodies. The resulting vortex brings up food particles along the floor of the stream to the filters that extend out the top of the larva. The number of examples of living things that use vortices to feed or to conserve energy as they travel seems to be endless.
How do these animals know to use the vortex effect? The way they position themselves and how they use the vortices in their environment works to their advantage. God’s elevator is a great testimony to His wisdom of design in the creation. We can know there is a God through the things He has made and how they use things like vortices to survive (Romans 1:20).
–John N. Clayton © 2018
Data from Discover, August 1993 page 81-87.